Yeah the scene between the two of them is very powerful. This episode confirms Gaiseric's lover was related to Danan in some form. But... it's hard to tell which exactly. The way she speaks about her doesn't feel like she was her daughter, and the way she talks to the Skull Knight doesn't make it seem like it was herself in another form either. That last hypothesis would have led to the assumption she had been reincarnated somehow, which has its own sets of problems (since the tree predated the grave).
So, all of this to say... a sister maybe?
Assuming she was an elf who could assume a human form, like Danan does. Of course there's also the issue of her title, that of "cherry blossom medium princess" basically. Someone important enough that she had Flora among her attendants. And related to a cherry tree, most likely the one she's interred under. Thinking about all this gave me a strange idea (i.e. very far-fetched) about how maybe humans could be born from spiritual trees. That could explain the uncanny resemblance between the priestess and Danan without her being an elf. It also brings to mind Schierke's origins, about which we know nothing.I do think the boy came to help reunite Guts and Casca. But I'm curious whether he'll truly talk to Guts this time, and if so, what he will have to say...
As for Griffith revealing himself, we'll see. I'm still not convinced Griffith could just take over whenever he wants, given that the boy has been shown to only be able to assume control under specific conditions. If that can be undone just because Griffith feels like it (and to achieve what?), then why even allow it in the first place? I think an outside element would be needed, like someone else trying to magically force the boy to "reveal" himself...
